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.TH UUENCODE 5
.SH NAME
uuencode \- format of an encoded uuencode file
.SH DESCRIPTION
Files output by
uuencode(1)
consist of a header line,
followed by a number of body lines,
and a trailer line.
The
uudecode(1)
command will ignore any lines preceding the header or
following the trailer.
Lines preceding a header must not, of course, look like a header.
.PP
The header line is distinguished by having the first 5 characters be
.I begin
followed by a space, or else a hyphen and either
.I base64
or
.I encoded
or both (also separated with a hyphen).
The
.I base64
option says the file has been encoded using base64.
The
.I encoded
option says the output file
.I name
has been base64 encoded.  It is never encoded with traditional uuencoding.
This is a GNU extension.
These are followed by a mode (in octal), and a string which names the
remote file.  The mode is separated from the
.I begin
clause and the file name by a single space character.
.SS "Traditional uuencoding"
.PP
The traditional
.I uuencoded
file body consists of a number of lines, each at most 62 characters
long (including the trailing newline). These consist of a character
count letter, followed by the encoded characters, followed by a newline.
The character count is a single printing character,
and represents an integer, the number of bytes
the rest of the line represents.
Such integers are always in the range from 0 to 63 and can
be determined by subtracting the character space (octal 40)
from the character.
.PP
Groups of 3 bytes are stored in 4 characters, 6 bits per character.
All are offset by a space to make the characters printing.
The last line may be shorter than the normal 45 bytes.
If the size is not a multiple of 3, this fact can be determined
by the value of the count on the last line.
Extra garbage will be included to make the character count a multiple
of 4.
The body is terminated by a line with a count of zero.
This line consists of one ASCII space.
.PP
The trailer line consists of
.I end
on a line by itself.
.PP
.SS "base64 encoding"
.I base64
encoded files follow the specified format for the body, but
also include a
.I begin-base64
header and a trailer line of four \fI=\fP characters.
.SH EXAMPLES
.nf
.na
.in +5
begin-base64-encoded 644 VE9ETw==
.in -5
.fi
.ad
This introduces a base64 encoded file named,
.I TODO
with that name encoded using base64 encoding.
.sp
.nf
.na
.in +5
begin-encoded 644 5$]$3P``
.in -5
.fi
.ad
This introduces an encoded file named,
.I TODO
with that name encoded using uuencoding.
The encoding is a lot less friendly.  Please prefer base64 encoding.
.SH CONFORMING TO
IEEE Std 1003.1, plus extensions
.sp
The
.I \-encoded
suffix to the
.I begin
header line is a GNU extension.  Recipients must have the GNU
.I uudecode
program to decode them.
.SH SEE ALSO
uuencode(1), uudecode(1), base64(1GNU)
.SH HISTORY
The
.I uuencode
file format appeared in BSD 4.0 .
